This invention relates generally to safety and child-proof closures adapted to be employed with containers for various types of fluids, including toxic and/or flammable liquids, and more particularly to locking cap constructions of the type intended to be held permanently captive on the dispensing container throughout substantially the entire life thereof.
In the past, a number of different safety screw cap constructions have been proposed and produced. Generally, where metal cans were employed as dispensing containers, the closure cap was constituted as a molded plastic part having an annular camming surface disposed adjacent to an annular retainer groove, such that the cap could be installed in the dispensing aperture of the container by merely forcing the camming surface thereof past the wall of the aperture. The aperture wall then became seated in the groove, completing the assembly. The fit between the cap and the walls of the dispensing aperture of the container was snug, whereby the cap was permanently retained by a sealing engagement that was effected, to minimize the possibility of leakage occurring.
With the advent of newer packaging concepts, there has been a shift away from the use of metal containers, and toward the use of the less costly, formed plastic types. This has created the need for different approaches, in order to accommodate the use of known locking closure caps as employed on plastic bottles or containers of existing designs or shapes. Generally, such plastic containers had neck portions of reduced diameter, externally threaded, with a standard thread of the type that is commonly known as "modified buttress", this being characteristic of the majority of plastic and glass containers in use today.
Generally, closure caps of the above type incorporated a closure plug or cover that was connected by means of a flexible hinge to the cap body, and that could be snapped into place on the body in a position to seal off one or more of the dispensing openings. The body was assembled to the dispensing container at the factory, in a manner that was intended to permanently hold it captive against either inadvertent displacement, or against intentional removal by the consumer, and particularly small children. Inadvertent removal of the cap body from the container was considered a hazard, since not only did there exist the possibility that the contents of the original container might be spilled or swallowed, but also such removal would tempt the adult consumer to re-fill the container with other substances which could be of a damaging or corrosive nature. Re-use of the container, as by re-filling, was thus considered to constitute a distinct danger, and accordingly, various attempts were made by manufacturers to discourage such activity.
Some prior cap constructions suffered from poor retention on the container, or poor sealing characteristics, or both. These devices therefore were unsatisfactory to the consumer from the standpoint of safety, particularly where either poisonous fluids were involved, or flammable liquids, such as charcoal lighter fluids and the like.
Cooperable interference lugs on the individual pieces of a two-part closure cap for a container have already been employed with moderate success, for holding captive one part of the cap and preventing its inadvertent removal. The problems with most all prior constructions, however, was that such lugs were difficult to incorporate into the molds for the various parts. The nature of the lugs, as well as the dimensions thereof, had to be such that they could readily by-pass one another and yet provide a positive retention against unscrewing and inadvertent removal. Sometimes the lugs interfered with the assembly of the closure cap, this often occurring where automatic screw capping equipment was being employed. When this occurred, either the equipment jammed, or the plastic parts were permanently damaged or otherwise deformed. In some instances, the nature of the lugs was such that a positive retention was not realized, and the safety closure function of the cap was thereby lost.
In prior constructions involving molded plastic containers, several attempts have been made in order to provide a seal between a molded closure cap and the outer surface of the small-diameter neck of the container. Due to the fact that in almost all cases there exists a parting line where two casing (container) halves meet, problems with obtaining an adequate seal have arisen, stemming from the discontinuity of the halves at this parting line. Accordingly, in almost all constructions involving sealing against the outer surface of the neck, leakage resulted. Such leakage was considered unacceptable in most cases, due to the potential hazards where toxic and/or flammable liquids were being packaged.